Browsing by Author "Amini, Seyed Hassan"

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    Design of Cell-Based Flotation Circuits under Uncertainty: A Techno-Economic Stochastic Optimization
    Amini, Seyed Hassan; Noble, Christopher Aaron (MDPI, 2021-04-27)
    The design of cell-based flotation circuits is often completed in two distinct phases, namely circuit structure identification and equipment sizing selection. While recent literature studies have begun to address the implications of stochastic analysis, industrial practice in flotation circuit design still strongly favors the use of deterministic metallurgical modeling approaches. Due to the complexity of the available mathematical models, most flotation circuit design techniques are constructed based on deterministic models. Neglecting the impact of various sources of uncertainty may result in the identification of circuit solutions that are only optimal in a narrow region of specific operating scenarios. One promising strategy to address this shortcoming is through the Sample Average Approximation (SAA) methodology, a stochastic approach to handling uncertainty that has been widely applied in other disciplines such as supply chain and facility location management problems. In this study, a techno-economic optimization algorithm was formulated to select the optimal size and number of flotation cells for a fixed circuit structure while considering potential uncertainty in several input parameter including feed grade, kinetic coefficients, and metal price. Initially, a sensitivity analysis was conducted to screen the uncertain parameters. After simplifying the optimization problem, the SAA approach was implemented to determine the equipment configuration (i.e., cell size and number) that maximizes the plant’s net present value while considering the range of potential input values due to parameter uncertainty. The SAA methodology was found to be useful in analyzing uncertainty in flotation kinetics; however, the approach did not provide a useful means to assess the influence of uncertainties in ore grade and metal price, as these values are not significant in determining equipment size but rather influence the optimal circuit structure, which was not considered in this study. Results from an application example indicate that the SAA approach produces optimal solutions not initially identified in a deterministic optimization, and these SAA solutions tend to provide greater robustness to uncertainty and variation in the flotation kinetics.
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    Vibration Enhanced Flooded Bed Dust Scrubber with Liquid-Coated Mesh Screen
    Uluer, Mahmud Esad (Virginia Tech, 2023-10-18)
    Respirable coal mine dust (RCMD) is one of the biggest occupational health hazards. Dusty mining environments can cause life-threatening respiratory health problems for coal miners known as black lung. Over the last 20 years, the flooded bed dust scrubber (FBS) has been employed as an integral component of dust control strategies for underground continuous mining operations. These units have been shown to be effective and robust in mining environments; however, several technical challenges and knowledge gaps limit their performance and efficiency. Despite the capability of the FBS, there are numerous technical challenges that limit its performance and efficiency. In particular, the static panel filter, instrumental in most scrubber designs, is fundamentally limited in collection efficiency and causes numerous operational challenges including rapid clogging. Furthermore, the current design of the filter panel is not capable of evenly wetting the entire surface area. This allows dust-laden air to pass through the filter media and decreases the cleaning capability of the FBS. In this research, both a lab-scale and a full-scale vibration-enhanced FBS with a liquid-coated filter panel were designed, manufactured, and tested. The results confirmed that a vibration-induced filter panel enhances dust collection performance and reduces mesh clogging. In addition, laboratory-scale mesh clogging tests showed that a hydrophilic mesh provided superior clogging mitigation and better performance. Typical results from bench-scale tests showed notable improvements in dust collection efficiencies by over 6% in wet condition and over 7% in dry condition while reducing mass accumulation in the filter by almost 10% in wet condition and over 40% in dry condition. The prototype testing was less conclusive, with deviations between the static mesh and vibrating mesh depending on the mesh density and operating conditions. Nevertheless, with the highest mesh density tested (30-layer), the vibrating mesh notably outperformed the static mesh with superior collection efficiency and reduced airflow loss. The system was further analyzed to investigate the size-by-size recovery of dust particles to various endpoints in the scrubber, under both vibrating and static conditions. Results show that while a majority of the particles are recovered into the demister sump, nearly a quarter of the dust mass is recovered upstream of the screen. In addition, the data confirm that vibration prompts notable improvements to collection efficiency, particularly in the finest size class (- 2.5 micron).